System and method for diagnosing a condition of an engine based on volcanic ash

ABSTRACT

A method and system for diagnosing a condition of an air-breathing aircraft engine are described. The method comprises obtaining a sample of lubricating fluid from the engine, filtering the sample to obtain a plurality of particles from the lubricating fluid, obtaining chemical composition data for the plurality of particles, determining a quantity of volcanic ash in the lubricating fluid by considering each one of the particles as composed partially of volcanic ash and partially of at least one other material and determining a first percentage of surface area of the particles covered by the volcanic ash and a second percentage of the surface area of the particles covered by the at least one other material, the volcanic ash having associated thereto a predetermined chemical composition, and diagnosing a condition of the engine based on the quantity of volcanic ash found in the lubricating fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/439,149 filed on Jun. 12, 2019, the contents of which arehereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to methods and systems fordiagnosing a condition of an engine, for example based on a level ofvolcanic ash in a lubricating fluid.

BACKGROUND OF THE ART

Volcanic ash ejected into the atmosphere by explosive eruptions can havedamaging effects on aircraft and their air-breathing engines. Ashparticles can abrade forward-facing surfaces, including windscreens,fuselage surfaces, and compressor and fan blades. Ash contamination canalso lead to failure of critical navigational and operationalinstruments. Moreover, the melting temperature of the glassy silicatematerial in an ash cloud is lower than combustion temperatures in modernaircraft engines. Consequently, ash particles sucked into an engine canmelt quickly and accumulate as solidified deposits in cooler parts ofthe engine.

Therefore, improvements are needed.

SUMMARY

In accordance with a first broad aspect, there is provided a method fordiagnosing a condition of an air-breathing aircraft engine. The methodcomprises obtaining a sample of lubricating fluid from the engine,filtering the sample to obtain a plurality of particles from thelubricating fluid, obtaining chemical composition data for the pluralityof particles, determining a quantity of volcanic ash in the lubricatingfluid by considering each one of the particles as composed partially ofvolcanic ash and partially of at least one other material anddetermining a first percentage of surface area of the particles coveredby the volcanic ash and a second percentage of the surface area of theparticles covered by the at least one other material, the volcanic ashhaving associated thereto a predetermined chemical composition, anddiagnosing a condition of the engine based on the quantity of volcanicash found in the lubricating fluid.

In accordance with another broad aspect, there is provided a system fordiagnosing a condition of an air-breathing aircraft engine. The systemcomprises at least one processor and a memory having stored thereonprogram code executable by the at least one processor for obtainingchemical composition data for a plurality of particles filtered from asample of lubricating fluid from the engine, determining a quantity ofvolcanic ash in the lubricating fluid by considering each one of theparticles as composed partially of volcanic ash and partially of atleast one other material and determining a first percentage of surfacearea of the particles covered by the volcanic ash and a secondpercentage of the surface area of the particles covered by the at leastone other material, the volcanic ash having associated thereto apredetermined chemical composition, and diagnosing a condition of theengine based on the quantity of volcanic ash found in the lubricatingfluid.

In accordance with yet another broad aspect, there is provided anon-transitory computer readable medium having stored thereon programcode executable by a processor for carrying out the methods describedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will becomeapparent from the following detailed description, taken in combinationwith the appended drawings, in which:

FIG. 1 illustrates an example of a gas turbine engine, in accordancewith some embodiments;

FIG. 2 is a block diagram of an example system for diagnosing acondition of an engine, in accordance with some embodiments;

FIG. 3 is a flowchart of an example method for diagnosing a condition ofan engine, in accordance with some embodiments;

FIG. 4 is a flowchart of an example method for determining a quantity ofvolcanic ash in a fluid sample, in accordance with some embodiments; and

FIG. 5 is a block diagram of an example computing device forimplementing a method for determining a level of volcanic ash inlubricating fluid, in accordance with some embodiments.

It will be noted that throughout the appended drawings, like featuresare identified by like reference numerals.

DETAILED DESCRIPTION

Volcanic ash can reach high into the atmosphere and intersect airspace.Violent eruptions can reach the tropopause (at about 40,000 ft) and evenpenetrate into the stratosphere. Aircraft often fly just below thetropopause. Volcanic emissions remain in the atmosphere for differentamounts of time, from hours to years, depending on the height theyinitially reach. It is estimated that 1 to 2% of all volcanic ashes willremain in suspension in the air, with the ashes having a diameterbetween 1-12 μm. Therefore, aircraft that fly over certain geographicalregions which comprise or are adjacent to one or more volcanos arelikely to take-in varying quantities of ash through the engine. Thevolcanic ash that enters through the engine of an aircraft may then makeits way into the lubricating fluid of the engine.

There are described herein methods and systems for determining aquantity of volcanic ash in a lubricating fluid of an air-breathingaircraft engine. These methods and systems may be used for enginediagnostics, in particular for gas turbine engines. In some embodiments,the methods and systems described herein may be used for optimizingroutes taken by aircraft in certain geographical regions, to reduceand/or minimize exposure of the aircraft to volcanic ash.

FIG. 1 illustrates an example of a gas turbine engine 10 to which themethods and systems described herein may be applied. Note that whileengine 10 is a turbofan engine, the methods and systems described hereinmay be applicable to turboprop, turboshaft, and other types of engines.Engine 10 generally comprises in serial flow communication: a fan 12through which ambient air is propelled, a compressor section 14 forpressurizing the air, a combustor 16 in which the compressed air ismixed with fuel and ignited for generating an annular stream of hotcombustion gases, and a turbine section 18 for extracting energy fromthe combustion gases. Axis 11 defines an axial direction of the engine10. In some embodiments, a low pressure spool is composed of a lowpressure shaft and a low pressure turbine 20. The low pressure shaftdrives the fan 12. A high pressure spool is composed of a high pressureturbine 22 attached to a high pressure shaft, which is connected to thecompressor section 14.

In some embodiments, the disclosed methods and systems may providediagnostic and analytical tools based on analysis of particles influids, such as engine oil or other lubricants and may provide advancedetection of premature wear on specific engine parts and/or detection offailure mechanisms. In some embodiments, the disclosed methods andsystems may be suitable for failure prediction for gas turbine enginesoperating in the field. The disclosed methods and systems may be usedfor prediction of other wear events including prediction of events otherthan failure using analysis of any suitable lubricating fluid of theengine. The disclosed methods and systems may also be used to detect anyabnormal behavior of an engine component in contact with a lubricationfluid system, for example.

FIG. 2 is a schematic diagram of an exemplary system 100 for diagnosinga condition of an engine such as the gas turbine engine 10 and whichuses a fluid for lubricating some of its components, such as bearings.System 100 comprises an engine diagnostic system 112 and suitable dataacquisition equipment 114 of known or other type. The engine diagnosissystem 112 may comprise one or more fluid analysis modules 116, such asa fluid analysis module configured to determine a level of volcanic ashin a fluid sample. In some embodiments, a separate fluid analysis module116 is provided to determine the level of each one of a plurality ofcomponents that may be found in a lubricating fluid.

The engine diagnosis system 112 and data acquisition equipment 114 maybe considered part of a workstation 122, such as for a Scanning ElectronMicroscope (SEM). Accordingly, data acquisition equipment 114 maycomprise an SEM and other related devices, although any other suitabledevices/methods for extracting the relevant information from particles124 filtered from lubricating fluid sample 126 may be used. In someembodiments, data acquisition equipment 114 may comprise an SEM and anX-Ray Fluorescence (XRF) detector for carrying out particle analysis.For example, data acquisition equipment 114 may comprise an automatedSEM, such as that from Aspex Corporation. In some embodiments, theautomated SEM may not require the presence of a human to select theparticle(s) 124 that will be analyzed. In some embodiments, softwareand/or hardware included in workstation 122 may automatically recognizethe presence of a particle 124 and may then automatically move a stageand/or an electron beam to the particle(s) 124 on which to perform theanalysis.

System 100 may be used to conduct analysis of particles 124 filteredfrom lubricating fluid sample 126. Data acquisition equipment 114 may beused to analyze filtered particles 124 and generate input data 128.Input data 128 may be processed using engine diagnosis system 112 inorder to generate output data 130. In some embodiments, output data 130may be representative of a diagnosis of the condition of the engine andmay be delivered to a user of system 100 or other authorized party viaoutput device(s) 132 (e.g., one or more screens and/or printers) fordisplaying and/or otherwise providing a report of the result(s) of thediagnosis. System 100 may include one or more input devices (e.g.,keyboard and mouse) for receiving user input, as well as one or moredata ports and/or communication ports for receiving and/or transmittingdata (e.g., wirelessly or through wired connections) from/to otherprocessors, systems and/or devices. Processing of input data 128 byengine diagnosis system 112 may make use of reference data forcomparison purpose. It is understood that processing of input data 128may be performed using one or more processors external to workstation122.

Referring to FIG. 3 , there is illustrated a flowchart of an examplemethod 300 for diagnosing a condition of an engine, such as engine 10.At step 302, a sample fluid is obtained. For example, a sample of usedlubricating fluid is obtained from the engine under diagnosis. In thecase of a fluid sample from an aircraft engine, the fluid sample may becollected by an aircraft operator. More than one sample may be obtained.The amount of fluid sample obtained (e.g., 25 mL or less) may beselected in order to obtain a certain number of particles. For example,it may be known or expected that a given engine should have a certaindensity of particles in the fluid after a certain number of operatinghours. The volume of fluid sample obtained may thus be determined inorder to obtain an optimal quantity of particles. The frequency ofsampling may be determined based on the operating hours per year, thematurity of the engine, the typical behavior of the engine type and/orthe history of unscheduled engine removal for that engine type, forexample. Any known or other engine fluid sampling method may be used,such as but not limited to pressurized line sampling, drop tubesampling, and drain port sampling.

At step 304, the sample of fluid is filtered to obtain a plurality ofparticles from the sample. Filtering may be performed using varioustechniques. For example, a collected fluid sample may be filtered usinga very fine filter, such as a 0.22 μm filter, in order to filter outeven very small particles (e.g., particles sized as small as 0.5 μm indiameter or smaller). Using such a filter, a sample of about 25 mL mayproduce a surface sample of about 16 mm in diameter. The particlesobtained may range in size from about 0.5 μm to about 1600 μm, forexample, although smaller or larger particles may also be obtained. Thevolume of fluid sample filtered and the size of the sample prepared mayvary, such as according to the number of particles in the fluid. Thevolume of fluid sample that is filtered may be determined based on thetype of engine and/or the expected normal levels of particles in thefluid. In some examples, the obtained density of particles may be 500particles per mm². Other densities may also be used.

At step 306 chemical composition data is obtained for the particles.Each particle of the sample may be analyzed, for example, using an SEMequipped to perform x-ray spectroscopy, although any other suitablemethods may also be used. A subset of the particles (e.g., 10% or less)may be analyzed while ensuring a good representation of the whole sampleis captured. The analysis of the subset may be normalized to reflect theresult for the full sample. For an average fluid sample, about 1500 to2000 particles may be analyzed. Suitable image analyzer software, suchas those conventionally used with SEM, may be used to collect data aboutparticle composition. Analysis of each particle may produce a respectiveset of data for that particle, for example there may be up to 70 datapoints for each particle, the data describing various features of theparticle (e.g., size, shape and composition, among others).

In some embodiments, obtaining the chemical composition data comprisesreceiving the chemical composition data from a data acquisition device,such as the SEM. In some embodiments, obtaining the chemical compositiondata comprises performing the acquisition of the data using a dataacquisition device, such as the SEM.

At step 308, a quantity of volcanic ash in the fluid sample isdetermined based on the chemical composition data, the volcanic ashhaving associated thereto a predetermined chemical composition. Eachparticle is considered as composed partially of volcanic ash andpartially of at least one other material, and the sample is analyzed todetermine the level of volcanic ash therein.

In some embodiments, the volcanic ash is considered as a first alloy andthe one or more other material making up the particle is considered as asecond alloy.

In some embodiments, volcanic ash is categorized according to its silicacontent. Mafic ash (e.g. basalt) has a silica content between about 45%and about 52% and is rich in the minerals of feldspar, pyroxene, andolivine group. Felsic ash (e.g. rhyolite) has a silica content aboveabout 69% and is rich in quartz and feldspar. Intermediate ash includes,for example, andesite (about 52% to about 63% silica) and dacite (about63% to about 69% silica). In addition to silica, volcanic ashes may becomposed of several oxides, such as ferrous, aluminum, magnesium,calcium, sodium, and several trace elements.

In some embodiments, volcanic ash is categorized according to itssource. Studies have shown that the basic composition of the ash fromMount St Helens consists of approximately 65% SiO₂, 18% Al₂O₃, 5%Fe_(t)O₃, 2% MgO, 4% CaO, 4% Na₂O, and 0.1% S. This chemical compositionis specific to the ash that comes from Mount St. Helens. The volcanicash from another volcano, for example from Mount Stromboli in Italy, maytherefore differ in chemical composition.

In order to determine a quantity of volcanic ash from a fluid sample, aspecific volcanic ash composition of interest may be selected. In someembodiments, more than one volcanic ash composition is of interest. Assuch, the fluid sample may be analyzed in order to find any one of aplurality of volcanic ash compositions of interest. The various volcanicash compositions may be predetermined and stored in one or more storagemediums, such as a memory, and accessed by the fluid analysis module116.

In some embodiments, some of the particles in the fluid sample arecomposed in part of volcanic ash. The overall quantity of volcanic ashis thus determined by considering what percentage of surface area of theparticles are covered by volcanic ash, and extrapolating from thatpercentage a mass of volcanic ash in the sample of fluid. An exampleembodiment is illustrated in FIG. 4 .

At step 402, the percentage of surface area covered by a first material(the volcanic ash) and at least one other material (another alloy) aredetermined using:100%=S ₁ +S ₂  (1)

S₁ is the percentage of volcanic ash and S₂ is the percentage of theother alloy making up the particle. For the purpose of the presentexample, it is assumed that the at least one other material correspondsto a second material. The values found for S₁ and S₂ may be measuredusing, for example, the data acquisition equipment 114 of theworkstation 122. In some embodiments, the surface of the particle iscovered by three or more alloys, including volcanic ash and two or moreother materials. In such cases, equation (1) as well as equations (2) to(6) found below may be adapted accordingly.

At step 404, the particle density is determined based on the percentagesof the first and second materials, and on the densities of the first andsecond materials:

$\begin{matrix}{D_{p} = {{\frac{s_{1}}{100} \times D_{1}} + {\frac{s_{2}}{100} \times D_{2}}}} & (2)\end{matrix}$

D₁ and D₂ are the densities of the first and second materials,respectively, and D_(p) is the density of the particle. The density D₁is a known value associated with the specific chemical composition forvolcanic ash. The density D₂ may be estimated based on the chemicalcomposition of the second material, as measured.

At step 406, the mass of the volcanic ash (or first material) for theparticle is determined based on the percentage of surface area of theparticle it covers, the density of the particle, and the particlegeometry. An estimated volume of the particle V_(p) may be found using:

$\begin{matrix}{V_{p} = \frac{{Area} \times {smallest}\mspace{14mu}{dimension} \times 3}{4}} & (3)\end{matrix}$

The Area corresponds to the total surface area of a particle, such as 10μm for a particle having dimensions of 2 μm×5 μm. The smallest dimensioncorresponds to the smallest of the two dimensions forming the Area, forexample 2 μm in the example of a particle having dimensions of 2 μm×5μm. With the volume (V_(p)) and the density (D_(p)) of the particle, themass (M_(p)) may be found using:M _(p) =V _(p) ×D _(p)  (4)

Using the mass of the particle, the mass of volcanic ash forming theparticle (M₁) may be found using:

$\begin{matrix}{M_{1} = {\frac{\frac{s_{1}}{100} \times D_{1}}{D_{p}} \times M_{p}}} & (5)\end{matrix}$

At step 408, the quantity of volcanic ash in the sample is determined asthe sum of the mass of volcanic ash for each particle:

$\begin{matrix}{{Volcanic}\mspace{14mu}{ash}\;{\left( \frac{mg}{L} \right) = {\frac{\sum\limits_{i = 1}^{n}\; M_{1_{i}}}{V_{s}} \times 1000}}} & (6)\end{matrix}$

V_(s) is the volume (in mL) of the fluid sample analyzed. Althoughprovided in mg/L, the mass of volcanic ash may be obtained in otherunits, such as g/L or g/mL, as will be readily understood.

In some embodiments, only a subset of the particles from the sample willcomprise volcanic ash. For the other particles, the value for S₁ will beset to zero and the result for M₁ will also be zero.

Referring back to FIG. 3 , at step 310, once the quantity of volcanicash in the fluid sample (or per given unit of fluid) is obtained, acondition of the engine may be diagnosed. The condition may comprise anumber of remaining flight hours for the engine, an expected need forengine maintenance, a level of impact of the volcanic ash on the engine,a reduction in efficiency of the engine (i.e. 10%, 25%, 50%, etc), areorganization of flight route, and the like.

Table 1 below is an example lookup table that may be used for enginediagnosis, for example by the engine diagnosis system 112.

TABLE 1 Quantity of VA Remaining Flight per unit of Hours before samplefluid next maintenance   0-5 mg/L   >500 hrs  6-10 mg/L 250-500 hrs11-15 mg/L   <250 hrs

Table 2 below is another example lookup table that may be used forengine diagnosis.

TABLE 2 Quantity of VA Level of impact per unit of VA on of sample fluidthe engine   0-5 mg/L Low  6-10 mg/L Medium 11-15 mg/L High

Reference data may be used to establish the impact of the volcanic ashon the engine. For example, reference engines from a common enginefamily having previously been exposed to a given level of volcanic ashmay be analyzed to obtain the reference data. In some embodiments, thereference data is presented as one or more averages for all referenceengines. The reference engines used for the reference data may form partof a common family with the engine under analysis. An engine family maybe defined by any engine characteristic, such as type, model, operatingprinciple, configuration, use, performance, thrust, torque, speed,power, etc. An engine family may also be defined by two or more enginefeatures. For example, a family may correspond to turboprop engines, orturboprop engines in use in aircraft, or turboprop engines in use inaircraft and weighing between 150 and 450 kg. In another example, afamily may correspond to a specific model or series, such as the PT-6Series from Pratt & Whitney Canada. In some embodiments, a family maycomprise sub-families, i.e. the family has at least one common enginecharacteristic and each sub-family has at least one additional commonengine characteristic. Various combinations may be used.

In some embodiments, the reference data is presented as a percentage ofselected engines matching one or more events. For example, out of 50reference engines selected, i.e. comprising a similar level of volcanicash per sample of lubricating fluid, the reference data may be presentedas: 100% operated 200 hours without any problems, 91% operated 500 hourswithout any problems, 73% operated 600 hours without any problems, 10%operated 750 hours without any problems. Other events may also be usedin this format.

In some embodiments, diagnosing a condition of the engine, as per step310, comprises assigning a rating to the engine. Various types of enginerating systems may be used, and comprise any number of rating levels,such as two, three, four, and more. The ratings may be associated withan expected time until maintenance, or an expected time until breakdown.The rating may be determined using only the reference data of thereference engines, or a combination of reference data of the referenceengines and historical/current data of the engine under analysis. Forexample, if the expected time until maintenance is 600 hours, theprobability of achievement will be 73% based on the reference engines.Other rating systems may readily apply.

In some embodiments, the condition of the engine is used to determinewhether an aircraft having a given engine should be deployed or not fora mission. In some embodiments, the condition of the engine is used todetermine the route to use for a given mission. In some embodiments, themethod 300 further comprises a step of taking a maintenance action basedon the diagnosing, such as but not limited to issuing a report on thelevel of volcanic ash in the engine, setting a flag indicating a needfor inspection, performing further inspection of the engine, and thelike.

FIG. 5 is an example embodiment of a computing device 500 forimplementing the engine diagnosis system 112 and/or the fluid analysismodule 116 described above. The computing device 500 comprises aprocessing unit 502 and a memory 504 which has stored thereincomputer-executable instructions 506. The processing unit 502 maycomprise any suitable devices configured to cause a series of steps tobe performed such that instructions 506, when executed by the computingdevice 500 or other programmable apparatus, may cause thefunctions/acts/steps specified in the methods described herein to beexecuted. The processing unit 502 may comprise, for example, any type ofgeneral-purpose microprocessor or microcontroller, a digital signalprocessing (DSP) processor, a CPU, an integrated circuit, a fieldprogrammable gate array (FPGA), a reconfigurable processor, othersuitably programmed or programmable logic circuits, or any combinationthereof.

The memory 504 may comprise any suitable known or other machine-readablestorage medium. The memory 504 may comprise non-transitory computerreadable storage medium, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Thememory 504 may include a suitable combination of any type of computermemory that is located either internally or externally to device, forexample random-access memory (RAM), read-only memory (ROM),electro-optical memory, magneto-optical memory, erasable programmableread-only memory (EPROM), and electrically-erasable programmableread-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. Memory504 may comprise any storage means (e.g., devices) suitable forretrievably storing machine-readable instructions 406 executable byprocessing unit 502. In some embodiments, the memory 504 stores one ormore specific chemical composition for volcanic ash. In someembodiments, the memory 504 stores reference data from referenceengines, and/or one or more lookup tables associating various levels ofvolcanic ash with corresponding engine conditions.

The methods and systems for diagnosing a condition of an engine and/orfor determining a level of volcanic ash in a fluid sample as describedherein may be implemented in a high level procedural or object orientedprogramming or scripting language, or a combination thereof, tocommunicate with or assist in the operation of a computer system, forexample the computing device 500. Alternatively, the methods and systemsfor diagnosing a condition of an engine and/or for determining a levelof volcanic ash in a fluid sample may be implemented in assembly ormachine language. The language may be a compiled or interpretedlanguage. Program code for implementing the methods and systems fordiagnosing a condition of an engine and/or for determining a level ofvolcanic ash in a fluid sample may be stored on a storage media or adevice, for example a ROM, a magnetic disk, an optical disc, a flashdrive, or any other suitable storage media or device. The program codemay be readable by a general or special-purpose programmable computerfor configuring and operating the computer when the storage media ordevice is read by the computer to perform the procedures describedherein. Embodiments of the methods and systems for diagnosing acondition of an engine and/or for determining a level of volcanic ash ina fluid sample may also be considered to be implemented by way of anon-transitory computer-readable storage medium having a computerprogram stored thereon. The computer program may comprisecomputer-readable instructions which cause a computer, or morespecifically the processing unit 502 of the computing device 500, tooperate in a specific and predefined manner to perform the functionsdescribed herein.

Computer-executable instructions may be in many forms, including programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc., that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the invention disclosed.Still other modifications which fall within the scope of the presentinvention will be apparent to those skilled in the art, in light of areview of this disclosure.

Various aspects of the methods and systems for detecting a fault may beused alone, in combination, or in a variety of arrangements notspecifically discussed in the embodiments described in the foregoing andis therefore not limited in its application to the details andarrangement of components set forth in the foregoing description orillustrated in the drawings. For example, aspects described in oneembodiment may be combined in any manner with aspects described in otherembodiments. Although particular embodiments have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from this invention inits broader aspects. The scope of the following claims should not belimited by the embodiments set forth in the examples, but should begiven the broadest reasonable interpretation consistent with thedescription as a whole.

The invention claimed is:
 1. A method for diagnosing a condition of anair-breathing aircraft engine, the method comprising: obtaining a sampleof lubricating fluid from the engine; filtering the sample to obtain aplurality of particles from the lubricating fluid; obtaining chemicalcomposition data for the plurality of particles; determining a quantityof volcanic ash in the lubricating fluid by considering each one of theparticles as composed partially of volcanic ash and partially of atleast one other material and determining a first percentage of surfacearea of the particles composed of the volcanic ash and a secondpercentage of the surface area of the particles composed of the at leastone other material, the volcanic ash having associated thereto apredetermined chemical composition; and diagnosing a condition of theengine based on the quantity of volcanic ash found in the lubricatingfluid.
 2. The method of claim 1, wherein the at least one other materialcomprises one second material, and wherein the first percentage and thesecond percentage correspond to about 100% of the surface area.
 3. Themethod of claim 1, wherein the predetermined chemical compositioncorresponds to a chemical composition for the volcanic ash associatedwith a geographical region.
 4. The method of claim 1, further comprisingdetermining a deployment of the aircraft engine based on the conditionof the engine.
 5. The method of claim 1, further comprising selecting aroute for a mission for the aircraft engine based on the condition ofthe engine.
 6. The method of claim 1, further comprising taking amaintenance action for the aircraft engine based on the condition of theengine.
 7. The method of claim 1, wherein determining the quantity ofvolcanic ash in the lubricating fluid comprises determining particledensity based on the first percentage and the second percentage and on adensity of the volcanic ash and a density of the at least one othermaterial.
 8. The method of claim 7, wherein determining the quantity ofvolcanic ash in the lubricating fluid comprises estimating a mass of thevolcanic ash per particle based on the first percentage and the secondpercentage, the particle density, and particle geometry.
 9. The methodof claim 8, wherein the geometry of the particle comprises a particlevolume V_(p) found using:${V_{p} = \frac{{Area} \times {smallest}\mspace{14mu}{dimension} \times 3}{4}};$where Area corresponds to a total surface area of a particle, andsmallest dimension corresponds to a smallest of two dimensions formingthe total surface area.
 10. A system for diagnosing a condition of anair-breathing aircraft engine, the system comprising: at least oneprocessor; and a memory having stored thereon program code executable bythe at least one processor for: obtaining chemical composition data fora plurality of particles filtered from a sample of lubricating fluidfrom the engine; determining a quantity of volcanic ash in thelubricating fluid by considering each one of the particles as composedpartially of volcanic ash and partially of at least one other materialand determining a first percentage of surface area of the particlescomposed of the volcanic ash and a second percentage of the surface areaof the particles composed of the at least one other material, thevolcanic ash having associated thereto a predetermined chemicalcomposition; and diagnosing a condition of the engine based on thequantity of volcanic ash found in the lubricating fluid.
 11. The systemof claim 10, wherein the at least one other material comprises onesecond material, and wherein the first percentage and the secondpercentage correspond to about 100% of the surface area.
 12. The systemof claim 10, wherein the predetermined chemical composition correspondsto a chemical composition for the volcanic ash associated with ageographical region.
 13. The system of claim 10, wherein the programcode is further executable for determining a deployment of the aircraftengine based on the condition of the engine.
 14. The system of claim 10,wherein the program code is further executable for selecting a route fora mission for the aircraft engine based on the condition of the engine.15. The system of claim 10, wherein the program code is furtherexecutable for taking a maintenance action for the aircraft engine basedon the condition of the engine.
 16. The system of claim 10, whereindetermining the quantity of volcanic ash in the lubricating fluidcomprises determining particle density based on the first percentage andthe second percentage and on a density of the volcanic ash and a densityof the at least one other material.
 17. The system of claim 16, whereindetermining the quantity of volcanic ash in the lubricating fluidcomprises estimating a mass of the volcanic ash per particle based onthe first percentage and the second percentage, the particle density,and particle geometry.
 18. The system of claim 17, wherein the geometryof the particle comprises a particle volume V_(p) found using:${V_{p} = \frac{{Area} \times {smallest}\mspace{14mu}{dimension} \times 3}{4}};$where Area corresponds to a total surface area of a particle, andsmallest dimension corresponds to a smallest of two dimensions formingthe total surface area.